Selective EMI Shielding Using Preformed Mask with Fang Design

ABSTRACT

A semiconductor device has a semiconductor package including a substrate comprising a land grid array. A component is disposed over the substrate. An encapsulant is deposited over the component. The land grid array remains outside the encapsulant. A fanged metal mask is disposed over the land grid array. A shielding layer is formed over the semiconductor package. The fanged metal mask is removed after forming the shielding layer.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor manufacturingand, more particularly, to a semiconductor device and method for formingselective electromagnetic interference (EMI) shielding using preformedmasks.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products.Semiconductor devices perform a wide range of functions such as signalprocessing, high-speed calculations, transmitting and receivingelectromagnetic signals, controlling electronic devices, transformingsunlight to electricity, and creating visual images for televisiondisplays. Semiconductor devices are found in the fields ofcommunications, power conversion, networks, computers, entertainment,and consumer products. Semiconductor devices are also found in militaryapplications, aviation, automotive, industrial controllers, and officeequipment.

Semiconductor devices are often susceptible to electromagneticinterference (EMI), radio frequency interference (RFI), harmonicdistortion, or other inter-device interference, such as capacitive,inductive, or conductive coupling, also known as cross-talk, which caninterfere with their operation. High-speed analog circuits, e.g., radiofrequency (RF) filters, or digital circuits also generate interference.

Conductive layers are commonly formed over semiconductor packages toshield electronic parts within the package from EMI and otherinterference. Shielding layers absorb EMI before the signals can hitsemiconductor die and discrete components within the package, whichmight otherwise cause malfunction of the device. Shielding layers arealso formed over packages with components that are expected to generateEMI to protect nearby devices.

One problem with prior art methods of semiconductor package shielding isthat forming the shielding layer over a package completely covers thetop of the package. Many semiconductor packages need open areas withexposed sockets or terminals that allow connection to adjacentsemiconductor devices, or need to have some components outside of theshielding layer to perform their proper function. Unfortunately,traditional shielding completely covers the packages and would shortcircuit any exposed terminals, sockets, or other exposed components.Tape masks have been used to form partially shielded packages. However,tape masks have complex process requirements to laminate the mask andthen peel the mask after sputtering. Therefore, a need exists forsemiconductor devices with selectively formed EMI shielding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a-1c illustrate a semiconductor wafer with a plurality ofsemiconductor die separated by a saw street;

FIGS. 2a-2m illustrate selectively forming a shielding layer using apreformed mask;

FIG. 3 illustrates a semiconductor device with the selectively formedshielding layer;

FIG. 4 illustrates a potential manufacturing defect that is likely tocause device malfunction;

FIGS. 5a-5c illustrate a preformed mask with a fang design alleviatingthe manufacturing defect;

FIGS. 6a-6e illustrate additional footprint profile shapes for the maskfangs; and

FIGS. 7a and 7b illustrate integrating the selectively shielded packagesinto an electronic device.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings. The term “semiconductor die” as used hereinrefers to both the singular and plural form of the words, andaccordingly, can refer to both a single semiconductor device andmultiple semiconductor devices. The terms “die” and “semiconductor die”are used interchangeably.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing involves the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer contains active and passive electrical components, which areelectrically connected to form functional electrical circuits. Activeelectrical components, such as transistors and diodes, have the abilityto control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, and resistors, create arelationship between voltage and current necessary to perform electricalcircuit functions.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual semiconductor die and packaging thesemiconductor die for structural support, electrical interconnect, andenvironmental isolation. To singulate the semiconductor die, the waferis scored and broken along non-functional regions of the wafer calledsaw streets or scribes. The wafer is singulated using a laser cuttingtool or saw blade. After singulation, the individual semiconductor dieare mounted to a package substrate that includes pins or contact padsfor interconnection with other system components. Contact pads formedover the semiconductor die are then connected to contact pads within thepackage. The electrical connections can be made with conductive layers,bumps, stud bumps, conductive paste, wirebonds, or other suitableinterconnect structure. An encapsulant or other molding compound isdeposited over the package to provide physical support and electricalisolation. The finished package is then inserted into an electricalsystem and the functionality of the semiconductor device is madeavailable to the other system components.

FIG. 1a shows a semiconductor wafer 100 with a base substrate material102, such as silicon, germanium, aluminum phosphide, aluminum arsenide,gallium arsenide, gallium nitride, indium phosphide, silicon carbide, orother bulk semiconductor material. A plurality of semiconductor die orcomponents 104 is formed on wafer 100 separated by a non-active,inter-die wafer area or saw street 106 as described above. Saw street106 provides cutting areas to singulate semiconductor wafer 100 intoindividual semiconductor die 104. In one embodiment, semiconductor wafer100 has a width or diameter of 100-450 millimeters (mm).

FIG. 1b shows a cross-sectional view of a portion of semiconductor wafer100. Each semiconductor die 104 has a back or non-active surface 108 andan active surface 110 containing analog or digital circuits implementedas active devices, passive devices, conductive layers, and dielectriclayers formed within or over the die and electrically interconnectedaccording to the electrical design and function of the die. For example,the circuit may include one or more transistors, diodes, and othercircuit elements formed within active surface 110 to implement analogcircuits or digital circuits, such as digital signal processor (DSP),ASIC, MEMS, memory, or other signal processing circuit. Semiconductordie 104 may also contain integrated passive devices (IPDs), such asinductors, capacitors, and resistors, for RF signal processing. Backsurface 108 of semiconductor wafer 100 may undergo an optionalbackgrinding operation with a mechanical grinding or etching process toremove a portion of base material 102 and reduce the thickness ofsemiconductor wafer 100 and semiconductor die 104.

An electrically conductive layer 112 is formed over active surface 110using PVD, CVD, electrolytic plating, electroless plating process, orother suitable metal deposition process. Conductive layers 112 includeone or more layers of aluminum (Al), copper (Cu), tin (Sn), nickel (Ni),gold (Au), silver (Ag), or other suitable electrically conductivematerial. Conductive layer 112 operates as contact pads electricallyconnected to the circuits on active surface 110.

Conductive layer 112 can be formed as contact pads disposed side-by-sidea first distance from the edge of semiconductor die 104, as shown inFIG. 1b . Alternatively, conductive layer 112 can be formed as contactpads that are offset in multiple rows such that a first row of contactpads is disposed a first distance from the edge of the die, and a secondrow of contact pads alternating with the first row disposed a seconddistance from the edge of the die. Conductive layer 112 represents thelast conductive layer formed over semiconductor die 104 with contactpads for subsequent electrical interconnect to a larger system. However,there may be one or more intermediate conductive and insulating layersformed between the actual semiconductor devices on active surface 110and contact pads 112 for signal routing.

An electrically conductive bump material is deposited over conductivelayer 112 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive layer 112 using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form conductive balls or bumps 114.In one embodiment, conductive bumps 114 are formed over an under-bumpmetallization (UBM) having a wetting layer, barrier layer, and adhesionlayer. Conductive bumps 114 can also be compression bonded orthermocompression bonded to conductive layer 112. Conductive bumps 114represents one type of interconnect structure that can be formed overconductive layer 112 for electrical connection to a substrate. Theinterconnect structure can also use bond wires, conductive paste, studbump, micro bump, or other electrical interconnect.

In FIG. 1c , semiconductor wafer 100 is singulated through saw street106 using a saw blade or laser cutting tool 118 into individualsemiconductor die 104. The individual semiconductor die 104 can beinspected and electrically tested for identification of KGDpost-singulation.

FIG. 2a illustrates a cross-section of an exemplary semiconductorpackage 150 prior to selectively forming a shielding layer.Semiconductor package 150 is a system-in-package (SiP) device in someembodiments. Substrate 152 includes one or more insulating layers 154interleaved with one or more conductive layers 156. Insulating layer 154is a core insulating board in one embodiment, with conductive layers 156patterned over the top and bottom surfaces, e.g., a copper-clad laminatesubstrate. Conductive layers 156 also include conductive viaselectrically coupled through insulating layers 154.

Substrate 152 can include any number of conductive layers 156 andinsulating layers 154 interleaved over each other. A solder mask orpassivation layer can be formed over either side or both sides ofsubstrate 152. Openings are formed in the passivation layer to exposecontact pads of conductive layer 156 for subsequent interconnection. Anysuitable type of substrate or leadframe is used for substrate 152 inother embodiments. Typically, packages 150 are formed on substrate 152as a panel large enough to form several to hundreds or thousands ofpackages at one time. Packages 150 are then singulated into individualpackages, of which FIG. 2a shows an example, by cutting throughencapsulant 168 and substrate 152.

Any components desired to be shielded in semiconductor package 150 aremounted to or disposed over substrate 152 within shielding area 160 andelectrically connected to conductive layers 156. A shielding interfacearea 161 is provided for connection of the subsequently formed shieldinglayer to ground strip 171 of conductive layer 156. A non-shielding area162 contains other components not intended to be shielded. FIG. 2aillustrates semiconductor die 104 mounted on substrate 152 along withdiscrete electrical components 164 within shielding area 160 as anexample. Discrete components 164 can be passive components such ascapacitors, resistors, or inductors, active components such as diodes ortransistors, or any other desired electrical component. Multiplesemiconductor die can be disposed in shielding area 160. Semiconductordie 104 can be provided as part of a smaller sub-package rather than abare die.

Semiconductor die 104 is mounted to substrate 152 by disposing thesemiconductor die on the substrate using, e.g., a pick-and-place processor machine, and then reflowing bumps 114 to physically and electricallyconnect the bumps to exposed contact pads of conductive layer 156.Discrete components 164 are connected by similar solder bumps or solderpaste 166. Solder paste 166 can be printed onto substrate 152 ordiscrete components 164 prior to picking and placing the discretecomponents onto the substrate. Reflowing solder paste 166 physically andelectrically couples discrete components 164 to contact pads ofconductive layer 156.

After mounting of semiconductor die 104, discrete components 164, andany other desired electrical components onto substrate 152 withinshielding area 160, the components are encapsulated by encapsulant ormolding compound 168. Encapsulant 168 is deposited over substrate 152,semiconductor die 104, and discrete components 164 using paste printing,compressive molding, transfer molding, liquid encapsulant molding,vacuum lamination, spin coating, or another suitable applicator.Encapsulant 168 can be polymer composite material, such as epoxy resin,epoxy acrylate, or polymer with or without a filler. Encapsulant 168 isnon-conductive, provides structural support, and environmentallyprotects the semiconductor device from external elements andcontaminants.

A mask or other mechanism can be used to prevent encapsulant 168 fromcovering shielding interface area 161 and non-shielding area 162. Inother embodiments, encapsulant 168 is deposited over shielding interfacearea 161 and non-shielding area 162 and then removed in thenon-shielding area. A passivation layer formed over the top of substrate152 can operate as an etch stop layer while removing the encapsulant innon-shielding area 162 and shielding interface area 161. Openings areformed in the passivation layer after encapsulant 168 is removed toexpose ground strip 171 and contact pads of land grid array 172.

Any electrical components that are desired to be left unshielded aredisposed on or over substrate 152 within non-shielding area 162.Non-shielding area 162 is populated with electrical components afterencapsulation with encapsulant 168 to reduce complexity of masking thenon-shielding area from being encapsulated. In other embodiments,components can be disposed on substrate 152 in non-shielding area 162prior to depositing encapsulant 168. Components in non-shielded area 162can include board-to-board connectors and other physical interfaces,antennae disposed over substrate 152 or formed as part of conductivelayers 156, additional discrete components 164, or any other desiredelectrical components.

In FIG. 2a , no components are disposed or formed in non-shielding area162 over substrate 152. Contact pads of conductive layer 156 are leftexposed as a land grid array 172 for electrical interconnection or foraddition of electrical components at a later stage. Another portion ofconductive layer 156 is left exposed in shielding interface area 161 asground strip 171. FIG. 2b shows a top-down plan view of ground strip 171and land grid array 172. Land grid array 172 provides exposed contactpads to electrically connect to semiconductor die 104 or the underlyingdevice that package 150 is incorporated into. The electrical connectioncan be made by soldering components or a physical port onto land gridarray 172, or a temporary connection can be made using a device withpogo pins or other suitable structure.

FIG. 2c shows a metal frame 200 and film 202 that will be used as acarrier during formation of a shielding layer over package 150. FIG. 2cincludes a top-down view on the left side of the figure and across-sectional view on the right side of the figure. FIGS. 2d, 2e, and2g similarly show both a top-down view and a cross-sectional view oftheir respective processing steps. Frame 200 can be formed of aluminum,copper, steel, or another suitable metal. Alternatively, frame 200 canbe formed from plastic, wood, or any other suitable rigid material. Atape or film 202 is mounted onto frame 200 to form a support base for aplurality of packages 150. Film 202 is formed from polyimide (PI) in oneembodiment. Film 202 has an adhesive coated on a surface of the film toallow the film to stick to metal frame 200 and to allow packages 150 toadhere to the film. The adhesive on film 202 can be a thermal orultraviolet (UV) release adhesive.

In FIG. 2d , a plurality of openings 204 is formed through film 202using laser cutting tool 206, a mechanical punch, or any other suitablemechanism. Openings 204 are smaller than the footprint of packages 150to allow the packages to be disposed on film 202 over the openings.Openings 204 facilitate removal of packages 150 from film 202 afterforming a shielding layer.

In FIG. 2e , packages 150 are disposed over openings 204 using apick-and-place process or machine. The bottom of substrate 152physically contacts film 202 all the way around opening 204 such thateach opening 204 is completely covered by a package 150. In oneembodiment, the overlap of substrate 152 over film 202 around opening204 is between 0.1 mm and 0.5 mm on each side of the substrate. In otherembodiments, openings 204 extend partially outside of the footprints ofpackages 150. Adhesive on film 202 sticks packages 140 to the film.

FIG. 2f shows a preformed mask 220 that will be placed overnon-shielding area 162 to block a shielding layer from being formeddirectly on the underlying components. Mask 220 includes sides 222,front 224, back 226, and top 228 that define a mask cavity 230. Each ofsides 222, front 224, and back 226 has a height in the Z-axis directionof the illustrated axis. Sides 222 have widths along the Y-axis andthicknesses along the X-axis. Front 224 and back 226 have widths alongthe X-axis and thicknesses along the Y-axis. Top 228 has a thicknessalong the Z-axis, a length along the X-axis, and a width along theY-axis.

Land grid array 172 is disposed in mask cavity 230 during formation ofthe shielding layer. Sides 222 and back 226 have heights that are atleast as high as the top of substrate 152. In embodiments withcomponents disposed on substrate 152 within non-shielding area 162, mask220 is made at least as tall as the tallest component withinnon-shielding area 162. The bottoms of sides 222 and back 226 can reston film 202 with top 228 extending over land grid array 172 or othercomponents. Front 224 has a bottom lip 232 that is raised higher thanthe bottoms of sides 222 and back 226 along the Z-axis. The openingunder lip 232 provides space for substrate 152 to extend from under mask220 to outside the mask.

Lip 232 contacts, or nearly contacts, the top surface of substrate 152while sides 222 and back 224 extend down to surround the end of thesubstrate with non-shielding area 162. The length of lip 232 along theX-axis is approximately the same or slightly longer than a width ofsubstrate 152 in the same direction so that sides 222 contact or nearlycontact the sides of the substrate. The widths of sides 222 are greaterthan a width of non-shielding area 162 so that back 226 sits justoutside a footprint of substrate 152 when lip 232 is placed on theborder between shielding interface area 161 and non-shielding area 162.

Mask 220 is formed of metal, liquid-crystal polymer (LCP), plastic,polymer, Teflon, glass, rubber, wood, film, tape, foil, combinationsthereof, or any other solid material that can withstand the process offorming a shielding layer. Mask 220 is formed by molding, by folding orworking a sheet of material into the desired shape, or by any othersuitable means.

FIGS. 2g-2i show packages 150 with masks 220 picked and placed overnon-shielding areas 162. FIG. 2g shows top-down and cross-sectionalviews, while FIG. 2h shows a perspective view and FIG. 2i shows adetailed top-down plan view. Mask 220 covers non-shielding area 162 toblock metal molecules from being deposited on land grid array 172 duringsputtering of a shielding layer. Shielding area 160 and shieldinginterface area 161 remain exposed for the formation of a shielding layerover those areas.

Land grid array 172, or any desired non-shielded electrical components,are disposed within cavity 230 of mask 220. The bottoms of sides 222 andback 226 rest on film 202. Lip 232 on the bottom of front 224 contactsor is slightly above the top surface of substrate 152. Top 228 extendsover the top of land grid array 172. The portion of substrate 152 withinnon-shielding area 162 extends between sides 222. Sides 222 and back 226are sized and positioned to contact or nearly contact substrate 152.

FIG. 2j shows another embodiment where packages 252 each have two landgrid arrays 172, one on each of two opposite sides of substrate 152. Twomasks 220 are used per package to mask both land grid arrays. When twomasks 220 of adjacent packages 252 are disposed directly adjacent toeach other, a space ‘X’ of at least 2 mm is maintained between themasks. Any number of land grid arrays or other components can be usedwith masks 220 shaped appropriately to cover all of the non-shieldedcomponents. Multiple masks are used when the components are disposed inmultiple groupings on substrate 152.

FIG. 2k , continuing from FIGS. 2g-2i , illustrates a conductivematerial being sputtered over packages 150, as indicated by arrows 262,to form a shielding layer 260. Shielding layer 260 is formed using anysuitable metal deposition technique, e.g., chemical vapor deposition,physical vapor deposition, other sputtering methods, spraying, orplating. The sputtered material can be copper, steel, aluminum, gold,combinations thereof, or any other suitable shielding layer material.Shielding layer 260 completely covers exposed surfaces of package 150and mask 220. In particular, all four side surfaces and the top surfaceof encapsulant 168 are covered by shielding layer 260 to surround theencapsulated components. Shielding layer 260 covers mask 220, but thesputtered metal does not penetrate the mask. Shielding layer 260 istherefore not formed directly on land grid array 172. All side surfacesof substrate 152 other than within mask 220 are covered by shieldinglayer 260.

The top surface of substrate 152 in shielding interface area 161,between encapsulant 168 and mask 220, is covered by shielding layer 260.The top surface of substrate 152 in shielding interface area 161includes exposed ground strip 171, or a plurality of discrete contactpads, of conductive layer 156 that shielding layer 260 physicallycontacts to provide an electrical connection to a ground voltage node.In some embodiments, a portion of conductive layer 156 is exposed at aside surface of substrate 152 so that shielding layer 260 physicallycontacts the conductive layer on the sides of the substrate as well.

In FIG. 2l , masks 220 are removed, including the portion of shieldinglayer 260 formed on the masks. Masks 220 can be removed using the samepick and place machine that placed the masks in FIG. 2h or using anyother suitable mechanism. With masks 220 removed, the area within frame200 remains completely covered in shielding layer 260 other thanopenings in the shielding layer around land grid array 172 where masks220 had been located.

Masks 220 are reusable, so the pick and place machine places the masksinto a tray or other suitable storage medium for later re-applicationonto the next set of packages to be shielded. Masks 220 may deteriorateafter multiple uses, or have another factor that limits the number oftimes an individual mask can be used. Testing can be done on aparticular mask design, and then each mask can be discarded after asuitable number of reuses determined via testing. A metal mask 220 cantypically be reused about thirty times.

Packages 150 are unloaded from frame 200 and film 202 in FIG. 2m . Anactuator 270 presses on the bottom of substrate 152 through openings 204to release packages 150 from the adhesive of film 202. A UV light orheat can be applied to reduce the effect of the adhesive between film202 and substrates 152. Actuator 270 can move from package to package inconcert with a pick and place machine that takes the lifted package 150and loads a JEDEC tray, tape and reel, or other similar storage mediumwith the shielded packages. Shielding layer 260 remains coveringencapsulant 168, a portion of the side surfaces of substrate 152, andthe top surface of the substrate within shielding interface area 161.

FIG. 3 shows an enlarged cross-section of a completed package 150.Shielding layer 260 surrounds semiconductor die 104 and discretecomponents 164 on all sides and on top. Shielding layer 260 extends downthe side surfaces of substrate 152 within shielding area 160 andshielding interface area 161. Shielding layer 260 covers the top surfaceof substrate 152 within shielding interface area 161, includingphysically contacting ground strip 171. Masks 220 have ensured thatshielding layer 260 does not cover the portion of substrate 152 withland grid array 172 so that the land grid array remains available forlater use.

In some embodiments, the bottom surface of substrate 152, oppositesemiconductor die 104, has solder bumps or another suitable interconnectstructure formed on contact pads of conductive layer 156 for attachingand connecting packages 150 to a larger PCB of an electronic device.Contact pads of conductive layer 156 can remain exposed on the bottomsurface as a bottom land grid array rather than adding anotherinterconnect structure. While the process illustrated uses a metal frame200 and film 202 as a carrier for packages 150 during formation ofshielding layer 260, any suitable type of carrier can be used, such as apanel of glass, aluminum, steel, copper, polymer, silicon, or anothersuitable material.

Mask 220 has the advantages of being simple and reducing costs.Simplicity is provided by using a mask that can be placed and removedusing common pick-and-place processing equipment. Cost is reduced byreusing mask 220. The overall process is streamlined by allowingnon-shielded components to be disposed on substrate 152 during the samemanufacturing stage as shielded components, e.g., semiconductor die 104.Prior art masking methods, e.g., tape masking, require thatnon-shielding area 162 remain free of components until after theshielding layer is formed and the mask is removed.

Depending on the exact tolerances of the manufacturing processes used tomake mask 220 and substrate 152, there may end up being a significantside gap between sides 222 of the mask and the sides of the substrate. Atop gap between the top surface of substrate 152 and lip 232 of mask 220may also be significant. For some manufacturing flows, sputtered metalmay undesirably infiltrate into non-shielding area 162 through the topand side gaps. In extreme cases, shielding layer 260 is formed undermask 220 far enough to physically contact some of the contact pads ofland grid array 172 as shown in FIG. 4. Having shielding layer 260unexpectedly short circuit part of land grid array 172 to ground strip171 is likely to cause malfunction of package 150.

Shielding layer 260 generally extends further toward land grid array 172at the sides of substrate 152, i.e., closer to the top and bottom in theorientation of FIG. 4, as compared to the middle of the substrate. Moresputtered metal is deposited under mask 220 at the sides of substrate152 because of the gap between the side of the substrate and sides 222of the mask in combination with the gap under lip 232.

FIGS. 5a and 5b show a mask 300 with a fanged design. FIG. 5a shows aperspective view and FIG. 5b shows a top-down view. Sides 222 of mask300 extend further toward shielding area 160 compared to mask 220, whilefront 224 remains on the border between shielding interface area 161 andnon-shielding area 162. The difference in position between front 224 andsides 222 along the y-axis results in a pair of fangs 302 formed betweensides 222 and front 224. The width of front 224 is reduced from 100% ofthe mask 220 width to between 70% and 90% of the mask 300 width. Theremaining width is made up by fangs 302. Front 224 and fangs 302 can beformed in any suitable proportion of the overall width of mask 300 inother embodiments. Lip 232 follows along front 224 and fangs 302 all theway to sides 222, creating a gap under the lip that is the same lengthalong the x-axis as in mask 220.

Fangs 302 move the front of mask 300 at the sides of substrate 152 awayfrom land grid array 172 and toward ground strip 171. The gap betweensides 222 of mask 300 and substrate 152 is moved away from land gridarray 172, which reduces the likelihood that sputtered metalinfiltrating into the side gap will reach the land grid array. Just themovement of the side gap further from land grid array 172 may besufficient to prevent shielding layer 260 from being formed in contactwith land grid array 172. In one embodiment, mask 220 is modified bylengthening sides 222 further toward shielding area 160 withoutmodifying front 224 and lip 232.

The additional reduction in sputtered metal through the top gap, betweensubstrate 152 and lip 232, depends on the widths of fangs 302. Thewidths of fangs 302 can be customized to affect a desired reduction insputtered metal at the sides of substrate 152. Widening fangs 302 moretoward the center of mask 300, and thereby reducing the width of front224, will result in a greater reduction in the likelihood of shieldinglayer 260 being formed in contact with land grid array 172. Fangs 302are each generally between 5 and 15 percent of the total width of mask300. In one embodiment, each fang 302 has a width that is 10% of theoverall mask 300 width, and front 224 occupies the remaining 80% of thewidth. Any suitable widths can be used in other embodiments.

FIG. 5c shows shielding layer 260 after being formed with mask 300.Fangs 302 push shielding layer 260 at the sides of substrate 152 awayfrom land grid array 172 and back toward shielding area 160. Sputteredparticles have further to travel from the side gap between substrate 152and mask 300 to land grid array 172, and therefore insufficientparticles are deposited to short circuit the land grid array to theshielding layer. Manufacturing defects are reduced by reducing thelikelihood of short circuit between shielding layer 260 and land gridarray 172.

FIGS. 6a-6e illustrate options for the footprint profile shape of maskfangs. The various fang shapes can be used to get more of astraight-line profile shape for the boundary of shielding layer 260between shielding interface area 161 and non-shielding area 162. Testingcan be done given a specific package to be shielded using givensputtering equipment and other manufacturing conditions to determine amask fang profile that results in an optimal shielding layer 260borderline for the given situation.

FIG. 6a shows the rectangular profile illustrated above. FIG. 6b showsmask 304 with a similar fang design. Front surfaces 306 of the fangs arerounded instead of planar. The curvature of front surfaces 306 can beconfigured as desired to modify the resultant shape of the shieldinglayer 260 border.

FIG. 6c shows a mask 310 with trapezoidal fangs. The trapezoidal fangscomprise outer side surfaces 312 a and 312 b, inner side surfaces 314 aand 314 b, and front surfaces 316 a and 316 b. The angles and lengths ofall six surfaces can be independently configured as desired to obtain adesired shape for the border of shielding layer 260.

FIG. 6d shows a mask 320 with triangular fangs. The triangular fangscomprise outer surfaces 322 a and 322 b and inner surfaces 324 a and 324b. Outer surfaces 322 a and 322 b are parallel to and continuous withsides 222. In other embodiments, outer surfaces 322 a and 322 b can beangled inward if desired. The angles and lengths of surfaces 322 a, 322b, 324 a, and 324 b can be configured to produce a desired shieldinglayer 260 borderline shape.

FIG. 6e shows a mask 330 with curved transitions 332 a and 332 b betweenfront fang surfaces 334 a and 334 b and front surface 224. Front fangsurfaces 334 a and 334 b are the same as in mask 300, and curvedtransitions 332 are added. Curved transitions 332 a and 332 b areillustrated as being concave arcs, but the transitions can be rounded ina convex manner, S-curves, straight lines, or any other suitable curveor shape. Transitions 332 a and 332 b can be mirror images of each otheras illustrated, or different curves can be used for the two transitions.Transitions 332 a and 332 b can be customized to achieve a desiredshielding layer 260 borderline.

FIGS. 7a and 7b illustrate incorporating the above described shieldedpackages, e.g., package 150 with shielding layer 260, into an electronicdevice. FIG. 7a illustrates a partial cross-section of package 150mounted onto a printed circuit board (PCB) or other substrate 402 aspart of an electronic device 400. Bumps 406 are formed on conductivelayer 156 on the bottom of substrate 152. Conductive bumps 406 can beformed at any stage of the manufacturing process, e.g., prior to moldingencapsulant 168, prior to singulation, or after forming shielding layer260. Bumps 406 are reflowed onto conductive layer 404 of PCB 402 tophysically attach and electrically connect package 150 to the PCB. Inother embodiments, thermocompression or other suitable attachment andconnection methods are used. In some embodiments, an adhesive orunderfill layer is used between package 150 and PCB 402. Semiconductordie 104 is electrically coupled to conductive layer 404 throughsubstrate 152 and bumps 406.

FIG. 7b illustrates electronic device 400 including PCB 402 with aplurality of semiconductor packages mounted on a surface of the PCB,including package 150 with shielding layer 260 and land grid array 172.Land grid array 172 can have an interconnect structure soldered to orpressed against the land grid array to connect package 150 to PCB 402,another package on PCB 402, another PCB of the same or differentelectronic device, another package on another PCB, another electronicdevice, testing equipment, etc. Land grid array 172 can also simply beleft exposed for subsequent temporary electrical connection to package150. Alternatively, other components instead of land grid array 172remain exposed to provide their intended function without shieldinglayer 260 interfering. Electronic device 400 can have one type ofsemiconductor package, or multiple types of semiconductor packages,depending on the application.

Electronic device 400 can be a stand-alone system that uses thesemiconductor packages to perform one or more electrical functions.Alternatively, electronic device 400 can be a subcomponent of a largersystem. For example, electronic device 400 can be part of a tabletcomputer, cellular phone, digital camera, communication system, or otherelectronic device. Electronic device 400 can also be a graphics card,network interface card, or another signal processing card that isinserted into a computer. The semiconductor packages can includemicroprocessors, memories, ASICs, logic circuits, analog circuits, RFcircuits, discrete active or passive devices, or other semiconductor dieor electrical components.

In FIG. 7b , PCB 402 provides a general substrate for structural supportand electrical interconnection of the semiconductor packages mounted onthe PCB. Conductive signal traces 404 are formed over a surface orwithin layers of PCB 402 using evaporation, electrolytic plating,electroless plating, screen printing, or other suitable metal depositionprocess. Signal traces 404 provide for electrical communication betweenthe semiconductor packages, mounted components, and other externalsystems or components. Traces 404 also provide power and groundconnections to the semiconductor packages as needed.

In some embodiments, a semiconductor device has two packaging levels.First level packaging is a technique for mechanically and electricallyattaching the semiconductor die to an intermediate substrate. Secondlevel packaging involves mechanically and electrically attaching theintermediate substrate to PCB 402. In other embodiments, a semiconductordevice may only have the first level packaging where the die ismechanically and electrically mounted directly to PCB 402.

For the purpose of illustration, several types of first level packaging,including bond wire package 446 and flipchip 448, are shown on PCB 402.Additionally, several types of second level packaging, including ballgrid array (BGA) 450, bump chip carrier (BCC) 452, land grid array (LGA)456, multi-chip module (MCM) 458, quad flat non-leaded package (QFN)460, quad flat package 462, and embedded wafer level ball grid array(eWLB) 464 are shown mounted on PCB 402 along with package 150.Conductive traces 404 electrically couple the various packages andcomponents disposed on PCB 402 to package 150, giving use of thecomponents within package 150 to other components on the PCB.

Depending upon the system requirements, any combination of semiconductorpackages, configured with any combination of first and second levelpackaging styles, as well as other electronic components, can beconnected to PCB 402. In some embodiments, electronic device 400includes a single attached semiconductor package, while otherembodiments call for multiple interconnected packages. By combining oneor more semiconductor packages over a single substrate, manufacturerscan incorporate pre-made components into electronic devices and systems.Because the semiconductor packages include sophisticated functionality,electronic devices can be manufactured using less expensive componentsand a streamlined manufacturing process. The resulting devices are lesslikely to fail and less expensive to manufacture resulting in a lowercost for consumers.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

1. A method of making a semiconductor device, comprising: providing asemiconductor package including, a substrate comprising a land gridarray, a component disposed over the substrate, and an encapsulantdeposited over the component, wherein the land grid array remainsoutside the encapsulant; disposing a fanged metal mask over the landgrid array, wherein the fanged metal mask includes a first fang at afirst side of the fanged metal mask and a second fang at a second end ofthe fanged metal mask, and wherein the first fang and second fang extendtoward the encapsulant; forming a shielding layer over the semiconductorpackage; and removing the fanged metal mask after forming the shieldinglayer.
 2. The method of claim 1, wherein the fanged metal mask includesa second fang with one of the first fang and second fang formed at eachside of the fanged metal mask.
 3. The method of claim 2, wherein thefangs include a rectangular shape in plan view.
 4. The method of claim2, wherein the fangs include a trapezoidal shape in plan view.
 5. Themethod of claim 2, further including configuring a shape of the fangs toproduce an approximately straight borderline of the shielding layer. 6.The method of claim 2, further including disposing the fanged metal maskwith the fangs oriented toward the encapsulant.
 7. A method of making asemiconductor device, comprising: providing a first semiconductorpackage comprising a substrate and an encapsulant deposited over only afirst portion of the substrate; disposing a fanged mask over a secondportion of the substrate after the encapsulant is deposited over thefirst portion of the substrate, wherein the substrate remains exposed ina gap between the fanged mask and encapsulant; forming a shielding layerover the encapsulant, wherein the shielding layer is formed on thesubstrate in the gap between the fanged mask and encapsulant; andremoving the fanged mask.
 8. The method of claim 7, wherein the fangedmask includes a pair of fangs with one fang formed at each side of thefanged mask.
 9. The method of claim 8, wherein the fangs include arectangular shape in plan view.
 10. The method of claim 8, wherein thefanged mask further includes a curved transition between each of thefangs and a front surface of the fanged mask.
 11. The method of claim 8,wherein the fangs include a rounded surface.
 12. The method of claim 8,further including configuring a shape of the fangs to produce anapproximately straight borderline of the shielding layer.
 13. The methodof claim 8, further including disposing the fanged mask with the fangsoriented toward the encapsulant.
 14. A method of making a semiconductordevice, comprising: providing a semiconductor package; disposing afanged metal mask over the semiconductor package; forming a shieldinglayer over the semiconductor package; and removing the fanged metalmask.
 15. The method of claim 14, wherein the fanged metal mask includesa pair of fangs with one fang formed at each side of the fanged metalmask.
 16. The method of claim 15, wherein the fangs include arectangular shape in plan view.
 17. The method of claim 15, wherein thefanged metal mask further includes a curved transition between each ofthe fangs and a front surface of the fanged metal mask.
 18. The methodof claim 15, wherein the fangs include a rounded surface.
 19. The methodof claim 15, wherein the fangs include a triangular shape in plan view.20. The method of claim 15, further including configuring a shape of thefangs to produce an approximately straight borderline of the shieldinglayer. 21-25. (canceled)
 26. A method of making a semiconductor device,comprising: providing a semiconductor package; disposing a fanged maskover the semiconductor package; and forming a shielding layer over thesemiconductor package.
 27. The method of claim 26, wherein the fangedmask includes a pair of fangs with one fang formed at each side of thefanged mask.
 28. The method of claim 27, wherein the fanged mask furtherincludes a curved transition between each of the fangs and a frontsurface of the fanged mask.
 29. The method of claim 27, wherein thefangs include a rounded surface.
 30. The method of claim 27, wherein thefangs include a triangular shape in plan view.